WHAT IS IT about the Karakoram Highway that brings out the macho in travelers, I wondered, as I watched our four-wheel drive being winched out of the snow.

For some, it would seem, it isn't enough just to travel this 1,300-kilometer route joining Kashgar, in China's Xinjiang Autonomous Region, with Rawalpindi and Islamabad in northern Pakistan. It has to be done under extreme physical conditions, preferably on a mountain bike, or on...